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Some analysis operations are resource-intensive and cannot process video frames as quickly as they can be ingested. For this reason, and because processing every frame does not necessarily improve detection performance or capture rates, analysis tasks usually do not process every frame of a video.
The interval at which an analysis task selects frames to be analyzed is called the sample interval. For example, if a task has a sample interval of 125 milliseconds then any two frames analyzed by the task will be separated by at least 125 milliseconds. This means that at most eight frames are analyzed for every second of video.
Media Server uses default sample intervals that have been chosen to produce good accuracy in most cases. HPE recommends using the default values but you can increase or decrease the sample interval for an analysis task by setting the
SampleInterval configuration parameter.
If you are processing a live stream, Media Server is ingesting video at a fixed rate and must keep up with the video. This means that if your Media Server does not have sufficient resources, it will not be able to process frames at the sample interval that you have requested. In this case, an analysis task will automatically increase its sample interval to ensure that analysis keeps up with the video. This might cause a reduction in accuracy because the frames that are analyzed will be further apart, making it more difficult for Media Server to track objects across frames and reducing the effectiveness of integration. When you are processing a live stream, you cannot change the rate at which video is ingested, so to prevent the sample interval being increased the only solution is to increase the resources (particularly CPU cores) available to Media Server.
If you are processing video that is ingested from a file, you can choose the rate at which video is ingested. The rate at which Media Server ingests video is controlled by the
IngestRate configuration parameter. You can set this parameter to one of the following values:
1 - This is the default value and must be used if you are processing a live stream. Media Server ingests video at normal (playback) speed. Assuming there are no external limitations such as network bandwidth, Media Server ingests one minute of video every minute. If an analysis task cannot process frames at the requested sample interval, it will automatically increase its sample interval and analyze fewer frames.
0 - The rate at which video is ingested is determined by the slowest analysis task that you have configured. The interval between the frames selected for analysis will always be as close as possible to
SampleInterval. Some analysis tasks are very fast, but some are slower and can analyze only one or two frames per second per thread. With
IngestRate=0, the amount of time required to ingest a video file depends on the analysis tasks that you have configured and the resources available to Media Server.
The sample interval and rate of ingestion have no effect on the speed at which a video frame is analyzed. The speed of analysis is determined by the resources available to Media Server. If your server has sufficient resources (CPU cores) and an analysis task supports it, you can set the
NumParallel parameter. This specifies the number of video frames for an analysis task to process concurrently. Processing frames in parallel can increase the total number of frames processed in a certain time. Depending on the ingest rate, this will either result in the actual sample interval being closer to the requested interval, or the file being processed in less time.
The following table summarizes the combinations that are available for
|Options||Default SampleInterval||SampleInterval = 0|
HPE recommends using
Media Server does not attempt to process every frame, but selects frames for analysis based on the specified sample interval. The default sample intervals should provide good accuracy in most cases. If necessary, Media Server will increase the sample interval to ensure that analysis occurs at normal (playback) speed.
If Media Server does not have sufficient resources, it will increase the sample interval, which might cause a reduction in accuracy.
Media Server attempts to analyze every frame, but frames are skipped if the analysis tasks you have configured cannot process the frames at normal (playback) speed.
HPE does not recommend these settings because processing every frame is usually not necessary and Media Server is likely to skip large numbers of frames.
Media Server does not attempt to process every frame, but selects frames for analysis based on the specified sample interval. The default sample intervals should provide good accuracy in most cases. If analysis is slow, Media Server ingests the file at a slower rate so that frames can be analyzed at the requested sample interval.
If Media Server does not have sufficient resources, it will take longer to process the file, but accuracy is maintained.
Ensures that all frames are analyzed.
HPE does not recommend these settings because in most cases this will take much longer and might not increase accuracy.
Use this mode only if it is critical that every frame is analyzed.